Your ProMaster Temperature Gauge is Lying to You! So I Installed an UltraGauge.

It’s no secret around here that we recently had a months-long bout of engine trouble with Lance. That’s been discussed to death elsewhere on the site (like HERE, and HERE), so I won’t rehash that. The one conclusion we received – from a technician who had disassembled Lance’s engine and tested individual parts – was that Lance’s thermostat had failed, and this led to a perpetual overheating situation that started the descent into ProMaster engine madness.

But here’s the thing: I had no way of knowing this. The ProMaster dashboard temperature gauge always shows the same thing… because it’s programmed that way. Don’t believe me? Watch this video! (And then see what I decided to do about it.)

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I was determined not to let something like this happen again (duh). Given that it’s impossible to get any meaningful information from a gauge that always shows the same thing, I needed a new solution. So I turned to the OBD2 code readers that are available today. I explain this in the video, but these are devices that plug into the “check engine light” port on your vehicle, and then can display information from your vehicle’s computer – in real time – to you in the cab. There are lots you can pick from – but these are the four I took seriously:

This was the first on my list because a Travato-driving buddy of ours uses one on his rig. In fact, you can see a picture of it in action in the comments on this post. This would be a very safe option, as it’s tried and true, and proven. I know several other ProMaster RV owners who have installed one and are happy with it. It DOES require an install – you have to run a cable and mount a display unit.

Yes, this thing is crazy expensive compared to the others. But it was recommended to me as “something that I can guarantee will work” by a friend who’s into race cars… Race Cars! Lance is a race car, right? Well not really. But this was useful to research as a top-tier unit, so I had something to compare other ones to.

In looking around at OBD2 monitors on Amazon, you’ll no doubt stumble across a number of Bluetooth solutions. Many of them are from offshore companies with names like “Zoomitech” that I wouldn’t totally trust. In the end, this is the one I wound up going with because of the reasons you’ll hear me go over in the video. I chose UltraGauge over some of the other imported solutions because UltraGauge is a US company (though the units themselves are manufactured in China).

Once I started looking at UltraGauge, I flirted with the idea of using one of their wired units – namely because they seem to have a good quality unit for a lower price. You might want a wired unit if you don’t want to worry about the latency of a Bluetooth solution. Or, if your Bluetooth connections from your smartphone are notoriously flaky and you don’t want to deal with something that ultimately becomes annoying due to connection problems.

The other thing I needed to complete the solution was a way to mount my phone. I decided to use something that I haven’t used in any vehicle in over a decade… the CD Player! I picked up this CD player mount for a smartphone from Amazon, and then I had everything you see in the video.

Oh – And About that Check Engine Light

I honestly didn’t plan or plant that check engine light you see in the video! But it does highlight one of the other super-cool benefits of the UltraGauge blue (as compared to a hard-wired unit). The smartphone app makes it extremely easy to see what’s causing a “Check Engine” light. I‘m not even in the van now, but I can still pull up the code on my smartphone. This is what I get:

And if I tap on the error code, it searches it on the web for me, and I get this information:

So now – later this afternoon – when I head to the RAM dealer to have it looked at, I know what to expect. (And if I were going to a dealership I didn’t trust, it would be a good way to check on them.) I should say that this information is usually available from any OBD2 code reader, but the smartphone app really takes the display of it to the next level, and I don’t have to be in the vehicle to recall it.

Well, that’s going to do it for now. I suspect this IAT thing is probably something that was fudged up during Lance’s recent heart transplant. But I guess we’ll see.

James is a former rocket scientist, a USA Cycling coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he works for a large IT company.

36 thoughts on “Your ProMaster Temperature Gauge is Lying to You! So I Installed an UltraGauge.”

Great article and timing. I had noticed on our last RV the gauges never changed. We just bought a new View and it doesn’t have gauges. We drove it home, about 250 miles, turned it off and the chassis battery was dead. I just now ordered the ScanGauge II. Thanks

Load speed and coolant temp on the main screen. A bunch of trp /fuel/mpg gauges. Intake air temp (now that it’s fixed). And instant MPG (which is different from what the dash says). Others are still in flux.

The gauge on the dash has no numbers. And it never moves!!! It shows the same value always. Even though, as I showed in the video, the temperature moves around a lot. The gauge is programmed to not respond to temperatures over a wide range, and just always show halfway. That’s neither useful nor accurate. They might as well have just put a warning light on there.

My 2016 Sprinter Airstream temperature gauge really works. I can tell when it is running hot or very hot in comparison to the normal running temperature. If it is very hot due to a high work load or a highish load under warm temps or I am driving very slow over wash board then when I speed up and/or the load is reduced I can see the temperature dropping (slowly) back to normal.

Just ordered the UG-wired. Opted for the wired for a few reasons — mainly, though, because I’m planning to replace the radio with one that uses ApplePlay/Android Play to let us use the phone GPS (instant updates, etc.) … didn’t want to have to do switching as much. Figure routing the wiring shouldn’t be too bad. Can probably still use the phone to look up codes … right?

Do you know if the way Promaster displays (or doesn’t) the temperature is the industry standard on other vehicles also? I rarely if ever see a temperature variation on the gauges of other vehicles I drive either. Maybe all our “modern” cars/trucks need an improved temperature gauge too.

Is there a factory listed temperature above which we should be concerned? You say 230, others say another temp. I would think Ram would have a number, no?

If I get around to it, I’ll try plugging the UltraGauge into some other vehicles, and see if they have “bogus” temperature gauges too. As far as a number that RAM says, I can ask next time I go in for service. But I suspect if RAM had a temperature number they were willing to share, they would have just given us a working gauge in the first place!

James – great video as usual. I started with a ScanGauge II on my Sprinter, but switched to a wired UltraGauge about four years ago. It is a great product that I use to monitor the Diesel Particulate Filter (DPF) regenerations on my 2012 Sprinter. I use a nine parameter display on my UG. Does the UG Blue give you instant access to all the engine parameters on your phone? That could be a real advantage.

A follow-up: It turns out the Ultra-Gauge products (there are several) only offer a set of industry standard measurements. If e.g. you want to monitor transmission temperature, which does not have an industry standard code, you won’t find it offered in the UG products as manufacturers also define proprietary codes, by vehicle & year, for many such measurements. UG does offer a ‘programmable’ UG code reader known as the UG ‘MX’ which can be programmed to read up to 8 of these proprietary codes. Disappointingly, they offer no detail info on these codes and the tech at your service center may have no idea what your specific make/model/year vehicle’s code is for a given proprietary code. UG directs customers to search vehicle forums for this info (which I previously have tried without success). Even more frustrating, UG has disabled their forum where this info was intended to be shared between users and potential customers.

Bottom Line: If you want one or more specific measurements that are not common industry standard codes, you’ll need those codes for your specific make/model/year vehicle before even programmable scanners like the UG MX can present the data for you.

Hi James, Does the UG-MX give you the transmission temp.? After searching some of these readers I see many say that if you leave the reader always “On” some of there gauges go haywire!? Also some say that it runs there battery down so far they have to jump it. If you drive every day it might not be a problem unless your battery is weak. Do any of these readers have a On/Off switch so you can leave it plugged in & can turn off the power? I have not seen any. On a Travato if you only drive it once or so a week, it might run the battery down.. Your thoughts?

It does not give transmission temp on the ProMaster out of the box. There is a programmable mode where you can enter specific parameters that might get you more information that’s not standard. Another commenter has done a good job describing this mode.

Thanks for identifying this. I would like to be proactive on this issue. Can you please identify the thermostat that needed replacing with part number? I realize that it may be a different part number based on model year but it will give us a starting reference.

So, the driving issue here is the “dummy” temp gauge that is common to all modern vehicles. And the “need” to watch/know the engine temp. And that implies knowing at all times what the temp is running? And the gauge and alarms are only available/working when the app is running and connected to the BT device? Are you planning on having the app running all the time??? And you have to have your smart phone in the vehicle and connected? Thinking maybe a dedicated display on all the time is needed?

As long as the phone is in the vehicle and powered on, I’m covered. (And I can’t imagine leaving on a trip without a phone.) The app does not have to be running, nor does the phone display have to be on. The phone does have to be powered up, but since we have two USB ports on the dash, that’s not really an issue. The adapter connects with my phone when the vehicle starts. It even makes an “engine starting” noise when it starts up (which will confuse you the first time if you’re not expecting it). From that point on, the alarms are active and I’m covered.

Although certainly the units with the dedicated display are a viable option. They’re just harder to move from vehicle to vehicle.

Just ordered my Ultragauge Blue with windshield mount directly from Ultragauge. The only thing Amazon carried was wired to a display and I just didn’t want to deal with yet more danglies than I already have to. The last one(s) I installed were the Battery Tender plug in to the battery. Since in the ProMaster that’s under the floor mats between the two front seats, I got tired of pulling up the Weathertech floor mat just to get to it. The one after that is for the dashboard install of the MidlandUSA GMRS micromobile unit and its magnetic mount 6 DB antenna. Enough danglies with the USB input for music and the audio in for the Pono Player. Of course the cooling fan and the 5 channel amp and subwoofer. Yes, there’s still room for me but I think the tech is starting to take over!

Several things. I have a new ProMaster and put in the ScanGauge I already have. It runs 190-212 most of the time..My Civic posts similar numbers, topping out when climbing steep hills at low speed. It seems like the car runs the cooling fans very sparingly, since it stays cooler taking hills at higher speeds. One concern is that the ProMaster’s manual says not to run any monitoring device on the OBD port: “• ONLY an authorized service technician should connect equipment to the OBD II connection port in order to read the VIN, diagnose, or service your vehicle. • If unauthorized equipment is connected to the OBD II connection port, such as a driver-behavior tracking device, it may: • Be possible that vehicle systems, including safety related systems, could be impaired or a loss of vehicle control could occur that may result in an accident involving serious injury or death.” I think that’s bull. So how hot is too hot? 220 maybe? Did you ask the technician? TFL Truck was doing a towing test on the Ike Gauntlet and they had a monitor in the tow vehicle and it was running 230 degrees. They never even mentioned it.

Yeah, I think that’s a play to try to scare people into going into their dealer. Or maybe it’s a ploy for them to deny warranty repairs to electronics? If you read that strictly enough, you couldn’t even take your ProMaster to a local auto repair shop that wasn’t “authorized”. (Man, I’m getting cynical…)

I’ve got my alarm set at 230. Lance normally runs at about 212 on the highway. He only gets over 220 when climbing. I’ll ask the tech what a good range is when I pick him up from the IAT thing.

I agree James. Pure profit motive and CYA at work on RAM’s part there with that statement. I suppose it is possible a poorly made reader could cause a problem. That’s why I also chose an UltraGauge Blue though. First they give you a gauge that is worse than an idiot light since it does nothing. Then they tell you not to do anything to get a better idea of what is really going on. Disappointing. I’ve got about 6K miles of use on my UltraGauge now with no ill effects.

I like the OBD scanners but I never use the one I bought because I’d have to run the output app on the phone to see the gauges and I’m usually using the phone for maps or music, etc. So one of the dedicated display units seems like a good thing to try, thank you.

James…PERFECT timing! First off, congrats on being prepared for the *next* engine issue, even if this one was disguised from you. I’ve just been researching OBD2 readers or scanners because I’d like to monitor my transmission temperature. Our ‘venerable’ Tahoe is our tow vehicle but only has a 4-speed transmission. With the engine screaming in 2nd gear recently while towing our trailer (we live in the Rockies) my bride – as is so often the case – asks just the right question: “How do you know the transmission isn’t overheating?” Thus, the scanner research.

I’d seen UltraGauge Blue on the Web and I’ll be digging into some product details from them. One suggestion for others who watch this: My first stop was the Chevy dealer, where I asked if my old Tahoe’s OBD2 port provides transmission temperature. ‘It does on our GM readers’ was the answer. So that’s one of the benefits of working with a U.S. company who offers product support. I now know the data is ‘there’. It’s just a matter whether this scanner looks for it, which I’ll ask the UltraGauge folks.

Condolences on the engine repair bill, James. No one has promised us that fun is always free…

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